AIIMS 2012 Physics Magnetic Dipole Assertion Reason Question
Assertion: A planar circular loop of area A and carrying current I is equivalent to magnetic dipole of dipole moment M = IA. Reason: At large distances, magnetic field of circular loop and magnetic dipole is same.
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
Assertion is true but Reason is false.
Both Assertion and Reason are false.
Correct Answer
Detailed Explanation
Magnetic field due to a circular loop carrying current I is given as B = μ_0/4π * 2πr^2/(r^2 + x^2)^3/2 where, r = radius of loop x = distance from centre of loop For large distances, (x >> r), B = μ_0/4π * 2IA/x^3 = μ_0/4π * 2M/x^3 where M = IA = magnetic dipole moment of current loop which is equal to the magnetic field due to magnetic dipole. Thus, the current loop can be considered as a magnetic dipole.
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